Corrosion Behavior of Carbon Steel Coated with a Zinc-Rich Paint Containing Aluminum Sulfate and Barium Oxide under Wet and Dry Cyclic Conditions

Abstract

The structure of corrosion products and the corrosion behavior of carbon steel coated with a zinc-rich paint containing two metallic compounds, Al₂（SO₄）₃ and BaO, were studied through a wet and dry cyclic corrosion test. After the corrosion test, a white corrosion product and a red iron rust formed on the surface of the zinc-rich paint coating without the two metallic compounds. In contrast, their formation was suppressed on the surface of the zinc-rich paint coated film containing the two metallic compounds. Moreover, the addition of a small amount of the metallic compounds to the coated film drastically decreased corrosion current density of the coated steel, accompanied with the decrease in corrosion potential. Structural analyses revealed that simonkolleite （Zn₅（OH）₈Cl₂・H₂O） containing Al and nano-phase BaSO₄ were formed in the zinc-rich paint coating incorporated with the metallic compounds. This novel structure of the corrosion products was considered to improve the protectiveness of the zinc-rich paint coating.